Increased capacity spherical lined bearings

ABSTRACT

A rotary system and method to control feathering movement of a rotor blade. The system having a yoke arm configured to rotate a rotor blade. A first bearing and a second bearing are utilized to secure the rotor blade to the yoke arm and are configured to restrict longitudinal and transverse movement, while allowing feathering movement of the rotor blade relative to yoke arm.

BACKGROUND

1. Field of the Invention

The present application relates generally to rotary systems, and morespecifically, to a tail rotary system having spherical lined bearings.

2. Description of Related Art

Conventional tail rotors are well known in the art for effectivelycontrolling yaw movement of a rotary aircraft. The tail rotor utilizes aplurality of rotor blades for creating thrust, and during flight, therotor blades tend to feather, thereby creating an undesired movementthat could cause the tail rotor to fail.

In some embodiments, conventional tail rotary systems include rotorblades that rigidly attach to the yoke arms. These embodiments areeffective in restricting rotor blade feathering movement; however, theembodiments are prone to failure due to the blade feathering stressesexerted on the yoke arm.

Although great strides have been made in the field of tail rotarysystems, many shortcomings remain.

DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are setforth in the appended claims. However, the invention itself, as well asa preferred mode of use, and further objectives and advantages thereof,will best be understood by reference to the following detaileddescription when read in conjunction with the accompanying drawings,wherein:

FIG. 1 is a side view of a rotary aircraft utilizing a rotary system ofthe present application;

FIG. 2-3 are oblique views of a tail rotor of the rotary aircraft;

FIG. 4 is a partial oblique view of a yoke arm of the tail rotor of FIG.2;

FIG. 5 is a cross-sectional view of the yoke arm of FIG. 4 taken at V-V;

FIG. 6 is a cross-sectional view of the yoke arm of FIG. 4 taken atVI-VI;

FIG. 7 is a top view of a spherical bearing of FIG. 4;

FIGS. 8A and 8B are cross-sectional views of the spherical bearing ofFIG. 6 shown operably associated with a mast; and

FIG. 9 is a flow chart depicting the preferred method.

While the system and method of the present application are susceptibleto various modifications and alternative forms, specific embodimentsthereof have been shown by way of example in the drawings and are hereindescribed in detail. It should be understood, however, that thedescription herein of specific embodiments is not intended to limit theinvention to the particular embodiment disclosed, but on the contrary,the intention is to cover all modifications, equivalents, andalternatives falling within the spirit and scope of the process of thepresent application as defined by the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Illustrative embodiments of the system and method are provided below. Itwill of course be appreciated that in the development of any actualembodiment, numerous implementation-specific decisions will be made toachieve the developer's specific goals, such as compliance withsystem-related and business-related constraints, which will vary fromone implementation to another. Moreover, it will be appreciated thatsuch a development effort might be complex and time-consuming, but wouldnevertheless be a routine undertaking for those of ordinary skill in theart having the benefit of this disclosure.

The tail rotary system of the present application overcomes commondisadvantages associated with conventional tail rotors by providingeffective means for controlling feathering forces created by the rotorblades attached thereto during flight. Specifically, the tail rotorincludes one or more bearings for securing the rotor blades to a yokearm of a hub retention system. The bearings are aligned in a linearfashion so as to prevent longitudinal and transverse movement of theblade relative to the yoke arm, yet allowing feathering movement of therotor blade. The bearings also include cutouts selectively positioned inthe bearing housing for increasing feathering movement.

The tail rotary system of the present application will be understood,both as to its structure and operation, from the accompanying drawings,taken in conjunction with the accompanying description. Severalembodiments of the system are presented herein. It should be understoodthat various components, parts, and features of the differentembodiments may be combined together and/or interchanged with oneanother, all of which are within the scope of the present application,even though not all variations and particular embodiments are shown inthe drawings. It should also be understood that the mixing and matchingof features, elements, and/or functions between various embodiments isexpressly contemplated herein so that one of ordinary skill in the artwould appreciate from this disclosure that features, elements, and/orfunctions of one embodiment may be incorporated into another embodimentas appropriate, unless described otherwise.

Referring now to the drawings wherein like reference characters identifycorresponding or similar elements throughout the several views, FIG. 1is a side view of a rotary aircraft 101 utilizing the tail rotary systemof the present application. Although depicted with the exemplary type ofrotary aircraft 101, it will be appreciated that the features disclosedherein are easily adaptable for use with other types of rotary aircraft.

Rotary aircraft 101 comprises a main rotary system 103 positioned abovefuselage 105 for rotating two or more rotor blades 107. The main rotarysystem 103 is controlled with a plurality of controllers carried withinfuselage 105. During flight, the cyclic controller 109 and/or pedal 111are manipulated to create vertical, horizontal, and yaw flightdirection. Aircraft 101 is further provided with a tail rotor 113 thatcreates yaw movement during flight. A detailed description of tail rotor113 is provided below.

Turning next to FIGS. 2 and 3 in the drawings, oblique views of tailrotor 113 according to the preferred embodiment of the presentapplication are shown. In the exemplary embodiment, tail rotor 113includes four rotor blades 201; however, it will be appreciated thattail rotor 113 is easily adaptable for use with more of less blades inan alternative embodiment. It should be understood that for clarity, oneof the four blades is removed to illustrate the bearings associated withthe tail rotor. Blades 201 are configured to couple with a hub retentionmember 203 having four yoke arms 205, which in turn is rotatablyattached to a mast 207 and an engine transmission 209.

Tail rotor 113 is further provided with two or more bearings: a firstbearing 211 and a second bearing 213, both bearings being configured toallow slight feathering movement of the rotor relative to the yoke arm.In the preferred embodiment, bearings 211 and 213 are spherical bearingsthat sit flush with an upper surface and a lower surface of yoke arm205; however, it will be appreciated that other types of bearings anddevices could be used in lieu of the preferred embodiment. As isdescribed more fully below, the spherical bearings allow for slightfeathering motion of the rotor blades, which provides significantadvantageous over conventional tail rotors, namely tail rotors havingrotor blades rigidly attached to the yoke arm.

Referring specifically to FIG. 3, yoke arm 205 has length extendingalong a longitudinal axis A1 and both bearings 211 and 213 havecenterlines C1 and C2, respectively, that are aligned in a linearfashion such that both centerlines C1 and C2 intersect with thelongitudinal axis A1 of yoke arm 205.

In FIG. 4, a partial oblique view of yoke arm 205 is shown. FIG. 4provides further illustration of the bearings according to the preferredembodiment of the present application. Tail rotor 113 preferablyincludes two bearings for securing the rotor blade to the yoke arm;however, it will be appreciated that alternative embodiments couldinclude additional bearings in lieu of the preferred embodiment. The twobearing configuration provides means for restricting transverse movementof the rotor blades in direction D1 and longitudinal movement indirection D2; however, the bearings are configured to allow slightfeathering movement of the rotor blades in direction D3 during flight.These features are achieved due to the alignment of the bearingsrelative to the yoke arm longitudinal axis A1, as described above.

In FIG. 5, a cross-sectional view of yoke arm 205 is shown taken at V-Vof FIG. 4. In the preferred embodiment, both bearings 211 and 213 arespherical bearings, which allow pivoting movement in direction D3 tocompensate for feathering. Bearing 211 comprises of a spherical ball 501rotatably engaged with a housing 503, and likewise, bearing 213comprises a spherical ball 505 rotatably engaged with a housing 507.Both bearings 211 and 213 include passages 509 and 511, respectively, asmeans for securing the blade thereto. In the preferred embodiment,housing 503 extends the entire thickness length of yoke arm 205,specifically, from a top surface 513 to a bottom surface 515. Thisfeature increases the contact surface area between housing 503 andspherical ball 501.

FIG. 6 is a cross-sectional view of yoke arm 205 taken at VI-VI of FIG.4. Bearing 211 is further provided with four cutouts extending from thetop and bottom surfaces of housing and inwardly into housing 503. Thecutouts are preferably contoured to match the outer contouring of theattachment means received by passage 509. It should be understood thatthe cutouts allow additional feathering movement of the rotor blades indirection D3, which in turn greatly increases the efficiency of bearing211. As is shown, bearing 211 preferably comprises four cutouts: a firstcutout 601 and a second cutout 603 extending from a top surface 605 ofhousing 503, and a third cutout 607 and a fourth cutout 609 extendingfrom a bottom surface 611 of housing 503.

In FIG. 7, a top view of bearing 211 is depicted. FIG. 7 furtherillustrates the contouring of cutouts 601 and 603. In the preferredembodiment, cutouts 601 and 603 have a generally circular contouring tomatch the contouring of the attachment means, i.e., a circular shaft.However, it will be appreciated that cutouts 601 and 603 could easily bemanufactured with different geometric contouring in alternativeembodiments. It should be understood that the cutouts are selectivelymachined on outer housing 503 to allow additional pivoting movement ofspherical ball 501 in direction D3 (feathering movement), but not indirection D2. It should be appreciated that the combination of bearings211 and 213 are utilized in conjunction with each other to preventmovement in directions D1 and D2, while allowing pivoting movement indirection D3. The cutouts are utilized to increase pivoting movement ofthe rotor blades during flight.

In FIGS. 8A and 8B, the bearings are shown operably associated with anattachment means 801, which in the preferred embodiment, is a shaft thatextends through passage 509. Attachment means 801 could include a linerplaced between the spherical ball 501 and attachment means 801 forproviding protection and support. As is depicted in FIG. 8B, phantomlines of attachment means 801 show feathering movement of the rotorblade relative to the yoke arm. It should be understood that attachmentmeans 801 does not come into contact with housing 503.

Referring next to FIG. 9, a flow chart 901 depicting the preferredprocess is shown. Box 903 shows the first step, which includes attachinga rotor blade to a yoke arm via a first bearing and a second bearing.The next step includes aligning the first bearing and the second bearingon the yoke arm to restrict both longitudinal and transverse movement ofthe rotor blade relative to the yoke arm, as depicted in box 905.Finally, box 907 shows the last step, which includes allowing pivotingmovement of the rotor blade relative with yoke arm to compensate forfeathering during flight.

It is apparent that a system and method with significant advantages hasbeen described and illustrated. The particular embodiments disclosedabove are illustrative only, as the embodiments may be modified andpracticed in different but equivalent manners apparent to those skilledin the art having the benefit of the teachings herein. It is thereforeevident that the particular embodiments disclosed above may be alteredor modified, and all such variations are considered within the scope andspirit of the application. Accordingly, the protection sought herein isas set forth in the description. Although the present embodiments areshown above, they are not limited to just these embodiments, but areamenable to various changes and modifications without departing from thespirit thereof.

What is claimed is:
 1. A method to control feathering movement of arotor blade, comprising: attaching the rotor blade to a yoke arm via afirst attachment means in a first bearing comprising a first pivotingelement and a first housing and via a second attachment means in asecond bearing comprising a second pivoting element and a secondhousing; forming a first aperture extending longitudinally through thefirst pivoting element along a centerline of the first bearing, thefirst attachment means extending longitudinally through the firstaperture; forming a second aperture extending longitudinally through thesecond pivoting element along a centerline of the second bearing, thesecond attachment means extending longitudinally through the secondaperture; aligning the first bearing and the second bearing on the yokearm in a linear fashion; limiting feathering to a first direction and asecond direction; intersecting the centerline of the first bearing witha longitudinal axis of the yoke arm at only a first point; intersectingthe centerline of the second bearing with the longitudinal axis of theyoke arm at only a second point; allowing pivoting movement of the rotorblade relative to the yoke arm along the first direction and seconddirection to compensate for feathering during flight; notching the firsthousing with a first set of notches to increase the feathering; notchingthe second housing with a second set of notches to increase thefeathering; and contouring the first set of notches and the second setof notches to correspond to an exterior surface of the first attachmentmeans and an exterior surface of the second attachment means,respectively, to increase the feathering.
 2. The method of claim 1,further comprising: restricting both longitudinal and transversemovement of the rotor blade relative to the yoke arm with the firstbearing and the second bearing.
 3. The method of claim 1, wherein thestep of aligning the first bearing and the second bearing on the yokearm in a linear fashion locates the first bearing and the second bearingon a plane.
 4. A rotary system, comprising: a yoke arm; a rotor blade; afirst bearing comprising a first pivoting element and a first housing,the first bearing being carried by the yoke arm and configured topivotally secure the rotor blade to the yoke arm; a second bearingcomprising a second pivoting element and a second housing, the secondbearing being carried by the yoke arm and configured to pivotally securethe rotor blade to the yoke arm; a first aperture extendinglongitudinally through the first pivoting element along a centerline ofthe first bearing, a first attachment means extending longitudinallythrough the first aperture; a second aperture extending longitudinallythrough the second pivoting element along a centerline of the secondbearing, a second attachment means extending longitudinally through thesecond aperture; four distinct cutouts located in the first housing; andfour distinct cutouts located in the second housing; wherein the rotorblade is pivotally secured to the yoke arm by the first attachment meansand the second attachment means; wherein the first bearing and thesecond bearing together allow feathering movement of the rotor bladerelative to the yoke arm during flight in only a first featheringdirection and a second feathering direction; wherein at least two of thefour distinct cutouts located in the first housing are contoured tocorrespond to an exterior surface of the first attachment means toincrease feathering; wherein at least two of the four distinct cutoutslocated in the second housing are contoured to correspond to an exteriorsurface of the second attachment means to increase feathering; whereinthe centerline of the first bearing intersects with a longitudinal axisof the yoke arm at only a first point; and wherein the centerline of thesecond bearing intersects with the longitudinal axis of the yoke arm atonly a second point.
 5. The rotary system of claim 4, wherein the firstbearing and the second bearing are both located on a plane.